We sailed on the Prima for 11 days this past March. We loved everything about our Haven experience. Admittedly we do not use the butler much, but the restaurant staff and the bar staff were the best we have ever had. We absolutely loved the pool at the back of the ship, and found it to be a much more social environment than other Haven pools. We met so many nice people, and would sail a Prima class ship again in a heartbeat. Of all the folks we met, we really didn't hear any major complaints, and the only complaints were about availability of the butlers, but nobody felt that it negatively impacted their time.
We are going on the Breakaway in January and we have been on that class ship before in the Haven and I know the pool area will not be the same, but we will love it as it is.